Semi-active roll stabilizer for small craft

ABSTRACT

An elongated liquid-housing stabilizing tank extending from port to starboard of a water-going vessel, particularly suited for small crafts such as yachts and fishing vessels. The tank is adapted to rotate about its major axis; and tank liquid is caused to transfer, by gravity, from one end of the tank to the other. The tank may be made to rotate at a constant speed or intermittently.

United States Patent [191 Pangalila [11] 3,826,212 [451 July 30, 1974 SEMI-ACTIVE ROLL STABILIZER FOR SMALL CRAFT Inventor: Frans V. A. Pangalila,

Waddinxveen, Netherlands Assignee: Flume Stabilization Systems, Inc.,

Hoboken, NJ.

Filed: Nov. 26, 1971 Appl. No.: 202,142

US. Cl. 114/125 Int. Cl B63b 43/06 Field of Search 114/121, 122, I24, 125;

References Cited UNITED STATES PATENTS 9/1971 Turci ll4/l25 Primary Examiner-George E. A. Halvosa Assistant ExaminerSherman D. Basinger Attorney, Agent, or Firm-Fleit, Gipple & Jacobson ABSTRACT 7 Claims, 3 Drawing Figures PATENIED M30 1974 MOTOR 6 m M D A .W m M u s m A AA 8 V I 2 c n llll pl-I 2 3 w m AK moztdsz INVENTOR ROLL ANGLE v FRANS V.A. PANGALILA FIG 3 ATTORN EYS SEMI-ACTIVE ROLL STABILIZER FOR SMALL CRAFT BACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION The present invention relates to a roll stabilizer particularly suited for use in small boats. The elongated stabilizing tank is adapted for rotation about its longitudinal axis thus bringing about the passive transfer of stabilizing liquid from one side of the tank to the other. The rotation of the stabilizer is done actively and, therefore, the problem of tuning the liquid flow to the high roll frequency of the boat is overcome. Because the tank liquid passively transfers in the tank, fans, pumps and other conventional and complex liquidmoving apparatus are unnecessary.

The stabilizing tank of the present invention is rotated by means of a motor which operates at either a constant speed or alternatively, in an intermittent fashion. Of course, with the constant speed operation, the control elements are simple. But, with the intermittent operation, the stabilizing liquid may be held, for a maximum time, in the positions wherein maximum stabilizing moments are developed.

The tank of the present invention comprises an elongated central compartment extending substantially from the port to the starboard of the associated boat. Integral end chambers are fitted at each end of the central compartment and have axes which define 90 angles with the longitudinal axis of the central compartment. The end chambers are aligned 180 out of phase with one another. Therefore, as the tank rotates about the longitudinal axis of the central compartment, the end chambers alternately adopt high and low positions. As a consequence of this arrangement, the tank liquid passes due to the force of gravity, from one end chamber to the other. And, in this manner, the static weight of the tank liquid is used to develop moments which oppose the roll of the associated boat.

In one embodiment of the present invention, the liquid level is set so as to just fill one of the end chambers when that chamber is facing in the downward direction. With this embodiment, therefore, the stabilized boat is only slightly heavier than the unstabilized boat.

In a second embodiment of the present invention, the level of the tank liquid is set so as to completely fill one of the end chambers and the central compartment. While the weight of this tank is substantially larger than the weight of the tank described in the preceding paragraph, the time involved in transferring the stabilizing moment from one end of the tank to the other is greatly decreased. Therefore, with the second embodiment, a more positive control of roll may be accomplished.

Accordingly, it is the main object of the present invention to provide a stabilizing tank for damping the roll of small boats.

It is another object of the present invention to provide a stabilizing tank for small boats which tank is actively controlled yet whose liquid passively flows from one end of the tank to the other.

It is still a further object of the present invention to provide a semi-active stabilizer for small boats which is relatively simple in design and relatively inexpensive to manufacture.

Yet another object of the present invention is to provide a semi-active stabilizer which operates both at a constant speed and intermittently.

These and other objects of the present invention, as well as many of the attendant advantages thereof, will become more readily apparent when reference is made to the following description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-section through the hull of a small boat showing one possible placement of a stabilizing tank designed in accordance with the teachings of the present invention;

FIG. 2 is a cross-section through a tank similar to that illustrated in FIG. 1, including an active control system, and having a liquid level in accordance with an alternate configuration of the present invention; and

FIG. 3 shows a series of curves illustrating the intermittent operation of the inventive stabilizing tank.

DETAILED DESCRIPTION OF THE DRAWINGS In FIG. 1, a small boat 10, such as a yacht, is shown equipped with a stabilizing tank 14 constructed in accordance with the teachings of the present invention. The tank 14 is adapted to rotate about an axis 16 and comprises basically an elongated central compartment 19 and a pair of end chambers 20 and 22. The axis 16 is the longitudinal central axis of the compartment 19. While the particular cross-sections of the chambers 19, 20 and 22 may vary according to design choice, a circular cross-section of these members is convenient. The tank 14 is filled, in part, with a stabilizing liquid the level of which is indicated at 18. The numeral 12 represents the center of roll of the boat 10, but it should be understood that the tank 14 may be located above the center of roll.

The operation of the tank 14 is as follows. As the boat 10 rolls about its center of rotation 12, the tank 14 is caused to rotate about its axis 16. The tank liquid attempts to minimize its potential energy by finding its way to the lowest position available; and, therefore, when the tank 14 is in the position shown in FIG. 1, the chamber 20 houses the tank liquid. When, however, the tank 14 rotates through the functions of chambers 20 and 22 are reversed. That is, the liquid will tend to fiow into chamber 22 leaving chamber 20 empty. Of course, it is important that the liquid be in the proper end chamber at the proper time-the liquid should occupy the chamber in which it developes a moment tending to oppose the roll of the boat. Therefore, the rotation of the tank 14 must be timed.

When the liquid from the FIG. 1 tank transfers from one end chamber to the other, several factors come into play. When this tank is rotated through 180, the force of gravity causes the liquid to fall from the chamber 20. The liquid then impacts the curved transition 23 between the end chamber 20 and the central compartment 19, and is urged toward the end chamber 22. Further, since the proper timing sequence requires that the liquid always travel downhill, gravity serves to assist the transfer of tank liquid.

With reference now to FIG. 2, the active driving system serving to rotate the tank 14' about its axis of rotation 16' will be described. A motor 24 is associated with the tank 14 in any conventional manner so that whenthe motor 24 is operative, the tank rotates about its major axis 16'. A sensing and command unit 26, capable of sensing the roll of the boat and controlling the operation of the motor 24 serves to positively dictate how and when the tank 14' should be rotated.

The tank of the present invention may be controlled in one of two ways. First, the motor 24 could rotate the tank at a constant speed so that the period of the tank and the period of the ship are substantially the same. This could be accomplished, in a conventional way, through the means of the sensing and command unit 26. Since it is desired that the position of the liquid lag the roll of the ship by 90, as is well known in the field, the sensing and command unit 26 should be so programmed. Alternatively, the tank may be rotated in an intermittent manner. That is, the sensing and command unit 26 may intermittently order that the motor 24 rotate the tank 19'. FIG. 3 illustrates the times at which the command unit 26 controls the operation of the motor 24.

In FIG. 3, three curves are shown, the curve 28 represents the roll of a ship in its unstabilized condition. Under ideal conditions, with the sea, boat and tank matched, the curve 30 represents the action of the tank liquid. The curve 32 is similar to the curve 30 but shows the operation of the tank forming a part of the present invention. Under ideal conditions, the tank liquid, represented by curve 30, lags the ship, represented by curve 28, by an angle of 90.

With the capability of intermittently controlling the rotation of the tank, a more advantageous use of the tank liquid may be accomplished. This is done by slightly varying from the above-discussed 90 phase relationship. The effective stabilizing moment developed by the tank liquid may be increased by alternately trapping the liquid in the end chambers and holding this liquid until a time shortly after the tank and boat pass through the horizontal. Such performance is fully described in US. Pat. application Ser. No. 645,723, filed on June 13, 1967, now abandoned, and assigned to the same assignee.

With continuing reference to FIGS. 2 and 3, the intermittent operation of the tank would be as follows. With the tank 14' rolling in a clockwise sense, the tank would be held in the position shown in FIG. 2 until shortly after the boat passes through its horizontal posi tion. Then, at a time a of curve 32, the tank would be made to turn through l80 so that the chamber 22' would fill with liquid, the chamber thereby being emptied. This condition would be maintained until the time b when the tank would, again, be turned through 180. Then, the procedure would be repeated at times c, d, e, and so forth.

It should be noted that the liquid level 18 shown in FIG. 1 differs from the liquid level 18 shown in FIG.

2. In FIG. 1, a relatively small amount of tank liquid is used. With such an amount, the tank liquid must actually traverse the entire length of the central compartment 19' in order to pass from one end chamber to the other. In FIG. 2, on the other hand, the amount of tank liquid is much greater. However, when this amount is used, the tank liquid need not pass through the central compartment 19 as was the case in the embodiment shown in FIG. 1. Rather, when the tank 19 is rotated 180 from the position shown in FIG. 2, the liquid near the chamber 22' merely spills into this chamber while the liquid in the chamber 20' moves only a small distance into the central compartment 19'. In this manner, the stabilizing moment may be transferred from one end of the tank to the other nearly instantaneously.

Above, several embodiments of the present invention have been described. It should be appreciated, however, that these embodiments are described for purposes of illustration only and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is the intent that the invention not be limited by the above but be limited only as defined in the appended claims.

I claim:

I. In combination with a water-going vessel, a stabilizing tank comprising: an elongated central compartment extending substantially from port to starboard of the associated vessel; a first end chamber integral with said elongated compartment, the axis of said first end chamber defining a angle with the longitudinal axis of said elongated central compartment; a second end chamber integral with said elongated compartment, the axis of said second end chamber defining a 90 angle with the longitudinal axis of said elongated central compartment, said first and said second end chambers being substantially out of phase with one another and thereby projecting from said central compartment in opposite directions; a stabilizing liquid partially filling said stabilizing tank; and means to rotate said stabilizing tank relative to said vessel about the longitudinal axis of said elongated central compartment.

2. The combination defined in claim 1, wherein the volume of stabilizing liquid is substantially equal to the volume of one of said end chambers.

3. The combination recited in claim 1, wherein the volume of stabilizing liquid is substantially equal to the volume of one of said end chambers added to the volume of said elongated central compartment.

4. The combination recited in claim 1, and further comprising a motor for rotating said stabilizing tank about the axis of said elongated central compartment at a uniform speed.

5. The combination recited in claim 1, and further comprising a motor for rotating said stabilizing tank intermittently so that the tank liquid alternately fills said end chambers.

6. The combination recited in claim 5, wherein the intermittent rotation of said stabilizing tank occurs shortly after the associated vessel passes through its horizontal orientation.

7. The combination recited in claim 1, wherein the period of rotation of the stabilizing tank is substantially equal to the period of roll of the associated vessel. 

1. In combination with a water-going vessel, a stabilizing tank comprising: an elongated central compartment extending substantially from port to starboard of the associated vessel; a first end chamber integral with said elongated compartment, the axis of said first end chamber defining a 90* angle with the longitudinal axis of said elongated central compartment; a second end chamber integral with said elongated compartment, the axis of said second end chamber defining a 90* angle with the longitudinal axis of said elongated central compartment, said first and said second end chambers being substantially 180* out of phase with one another and thereby projecting from said central compartment in opposite directions; a stabilizing liquid partially filling said stabilizing tank; and means to rotate said stabilizing tank relative to said vessel about the longitudinal axis of said elongated central compartment.
 2. The combination defined in claim 1, wherein the volume of stabilizing liquid is substantially equal to the volume of one of said end chambers.
 3. The combination recited in claim 1, wherein the volume of stabilizing liquid is substantially equal to the volume of one of said end chambers added to the volume of said elongated central compartment.
 4. The combination recited in claim 1, and further comprising a motor for rotating said stabilizing tank about the axis of said elongated central compartment at a uniform speed.
 5. The combination recited in claim 1, and further comprising a motor for rotating said stabilizing tank intermittently so that the tank liquid alternately fills said end chambers.
 6. The combination recited in claim 5, wherein the intermittent rotation of said stabilizing tank occurs shortly after the associated vessel passes through its horizontal orientation.
 7. The combination recited in claim 1, wherein the period of rotation of the stabilizing tank is substantially equal to the period of roll of the associated vessel. 